Optical system production system

ABSTRACT

Mounting and alignment structures for optical components allow optical components to be connected to an optical bench and then subsequently aligned, i.e., either passively or actively, in a manufacturing or subsequent calibration or recalibration, alignment or realignment processes. The structures comprise quasi-extrusion portions. This portion is “quasi-extrusion” in the sense that it has a substantially constant cross section in a z-axis direction as would be yielded in an extrusion manufacturing process. The structures further comprise at least one base, having a laterally-extending base surface, and an optical component interface. At least one armature connects the optical component interface with the base. In the preferred embodiment, the base surface is securable to an optical bench.

RELATED APPLICATIONS

[0001] This application is a divisional application of U.S. applicationSer. No. 09/645,827, filed on Aug. 25, 2000 (incorporated herein by thisreferences), which application claims the benefit of the filing date ofU.S. Provisional Application No. 60/165,431, filed Nov. 15, 1999, whichis incorporated herein by this reference in its entirety. Thisapplication also claims the benefit of the filing date of U.S.Provisional Application No. 60/186,925, filed Mar. 3, 2000, which isincorporated herein by this reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] Component alignment is of critical importance in semiconductorand/or MEMS (micro electromechanical systems) based optical systemmanufacturing. The basic nature of light requires that light generating,transmitting, and modifying components must be positioned accuratelywith respect to one another, especially in the context offree-space-optical systems, in order to function properly andeffectively in electro-optical or all optical systems. Scalescharacteristic of semiconductor and MEMS necessitate sub-micronalignment accuracy.

[0003] Consider the specific example of coupling a semiconductor diodelaser, such as a pump laser, to a fiber core of a single mode fiber.Only the power that is coupled into the fiber core is usable tooptically pump a subsequent gain fiber, such as a rare-earth doped fiberor regular fiber, in a Raman pumping scheme. The coupling efficiency ishighly dependent on accurate alignment between the laser output facetand the core; inaccurate alignment can result in partial or completeloss of signal transmission through the optical system.

[0004] Moreover, such optical systems require mechanically robustmounting and alignment configurations. During manufacturing, the systemsare exposed to wide temperature ranges and purchaser specifications canexplicitly require temperature cycle testing. After delivery, thesystems can be further exposed to long-term temperature cycling andmechanical shock.

[0005] Solder joining and laser welding are two common mountingtechniques. Solder attachment of optical elements can be accomplished byperforming alignment with a molten solder joint between the element tobe aligned and the platform or substrate to which it is being attached.The solder is then solidified to “lock-in” the alignment. In some cases,an intentional offset is added to the alignment position prior to soldersolidification to compensate for subsequent alignment shifts due tosolidification shrinkage of the solder. In the case of laser welding,the fiber, for example, is held in a clip that is then aligned to thesemiconductor laser and welded in place. The fiber may then also befurther welded to the clip to yield alignment along other axes.Secondary welds are often employed to compensate for alignment shiftsdue to the weld itself, but as with solder systems, absolutecompensation is not possible.

[0006] Further, there are two general classes of alignment strategies:active and passive. Typically in passive alignment of the opticalcomponents, registration or alignment features are fabricated directlyon the components or component carriers as well as on the platform towhich the components are to be mounted. The components are then mountedand bonded directly to the platform using the alignment features. Inactive alignment, an optical signal is transmitted through thecomponents and detected. The alignment is performed based on thetransmission characteristics to enable the highest possible performancelevel for the system.

SUMMARY OF THE INVENTION

[0007] The problem with conventional optical system production processesis that they require very specialized machines to implement andtypically produce marginal quality components quickly or high qualitycomponents slowly.

[0008] The reason for the discrepancy between speed and quality is thetypes of alignments that are performed. Passive alignment can beperformed quickly, but the resulting alignment is typically sub optimal.Active alignment is accurate, but slow.

[0009] The present invention is directed an optical system productionsystem. It utilizes passive placement of the optical components on anoptical bench followed by a preferably fast active alignment process. Inthis way, it seeks to capture the best features offer by conventionalalignment systems.

[0010] In general, according to one aspect, the invention features anoptical system production line. The line comprises an optical benchsupply that provides optical benches and a component supply thatprovides optical components. A pick-and-place machine receives opticalbenches and picks optical components from the optical component supply,and then places the optical components on the optical benches. It thensecures the optical components to the bench. Optical system aligner thencharacterizes the positions of the optical components on the opticalbench and mechanically adjusts the relative positions of the opticalcomponents.

[0011] In the preferred embodiment, the pick-and-place machine securesthe optical components to the bench by solder bonding. In the currentimplementation, the pick and place machine is a flip-chip bonder.Further, the optical system aligner characterizes the positions of theoptical components by activating an optical link of the optical system,detecting an optical signal after interaction with at least some of theoptical components, and adjusting the optical components to optimizetransmission of the optical signal over the link. The alignment systempreferably comprises two jaws for engaging a mounting structuresupporting the optical component and moving the structure relative tothe bench.

[0012] The above and other features of the invention including variousnovel details of construction and combinations of parts, and otheradvantages, will now be more particularly described with reference tothe accompanying drawings and pointed out in the claims. It will beunderstood that the particular method and device embodying the inventionare shown by way of illustration and not as a limitation of theinvention. The principles and features of this invention may be employedin various and numerous embodiments without departing from the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In the accompanying drawings, reference characters refer to thesame parts throughout the different views. The drawings are notnecessarily to scale; emphasis has instead been placed upon illustratingthe principles of the invention. Of the drawings:

[0014]FIG. 1 is a perspective view of a first embodiment of a mountingand alignment structure according to the present invention;

[0015]FIG. 2 is a front plan view of the first embodiment mounting andalignment structure;

[0016]FIG. 3A is a perspective view showing a second embodiment of themounting and alignment structure according to the present invention;

[0017]FIG. 3B is a front plan view showing the dimensions of the secondembodiment structure;

[0018]FIG. 4 is a perspective view showing a third embodiment of themounting and alignment structure according to the present invention;

[0019]FIG. 5A is front plan view showing fourth embodiment of theinventive mounting and alignment structures;

[0020]FIG. 5B is perspective view showing a related embodiment of theinventive mounting and alignment structures;

[0021]FIG. 6 is front plan view showing fifth embodiment of theinventive mounting and alignment structures;

[0022]FIG. 7 is a front plan view of a sixth embodiment of the mountingand alignment structures accounting to the present invention;

[0023]FIG. 8 is a front plan view of a seventh embodiment of theinventive mounting and alignment structures;

[0024]FIGS. 9 and 10 show eighth and ninth embodiments of the inventivemounting and alignment structures;

[0025]FIG. 11 is a front plan view of a tenth embodiment of theinventive mounting and alignment structures in which separate structuresare integrated onto a single base according to the invention;

[0026]FIG. 12 is a plan view showing an eleventh embodiment of amounting and alignment structure according to the present invention;

[0027]FIG. 13 is a plan view showing twelfth embodiment of the presentinvention;

[0028]FIG. 14 is a plan view showing a thirteenth embodiment of aninventive mounting and alignment structure for passive componentalignment;

[0029]FIGS. 15A and 15B are front plan views showing the fourteenthembodiment of the mounting and alignment structure and it deployment formounting a second optical component in proximity to another opticalcomponent;

[0030]FIGS. 16A, 16B, 16C are cross-sectional views of the plating andlithography processes used to fabricate the mounting and alignmentstructures according to the invention;

[0031]FIGS. 17A-17F illustrate a process for manufacturing mounting andalignment structures that have non-constant cross-sections along az-axis for portions of structures;

[0032]FIGS. 18A and 18B are a perspective diagram illustrating theprocess steps associated with installing optical components on themounting and alignment structures and mounting and alignment structureson the optical bench;

[0033]FIG. 19 is a perspective drawing of a laser optical signal sourcethat couples a beam into an optical fiber held by a mounting andalignment structure, according to the present invention;

[0034]FIG. 20 is a process diagram illustrating the optical systemactive alignment process according to the present invention;

[0035]FIG. 21 is a perspective top view showing the jaws of an alignerengaging the handle of a mounting and alignment structure to deform thestructure during an alignment process;

[0036]FIG. 22 is a plot of force and optical response on the verticalaxis as a function of displacement or strain on the horizontal axisillustrating the inventive alignment process;

[0037]FIG. 23 is the plot of force along the y-axis as a function ofdisplacement illustrating constraints in the selection of the yieldforce;

[0038]FIG. 24 is a perspective view showing a fifteenth, compositestructure embodiment of the invention;

[0039]FIG. 25 is a schematic perspective view of a sixteenth, dualmaterial embodiment of the invention;

[0040]FIG. 26 is a schematic diagram illustrating a production line foroptical systems, according to the present invention; and

[0041]FIGS. 27A, 27B, and 27C are partial plan views of the mounting andalignment structures showing three different configurations for thealignment channels.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] Mounting and Alignment Structure Configuration

[0043]FIG. 1 shows an exemplary mounting and alignment structure, whichhas been constructed according to the principles of the presentinvention.

[0044] Generally, the alignment structure 100 comprises a base 110, anoptical component interface 112, and left and right armatures 114A,1141B, which either directly connect, or indirectly connect, the base110 to the interface 112.

[0045] The base 110 comprises a laterally-extending base surface 116. Inthe illustrated example, the base surface 116 extends in a plane of thex and z axes, generally.

[0046] The base/base-surface comprise alignment features. In someembodiment, these features are adapted to mate with preferablyopposite-gendered alignment features of an optical bench. In thespecific illustrated implementation, the alignment features are used bymachine vision to match to alignment marks or features of a bench.Specifically, the alignment features comprise a wide, U-shaped cut outregion 120. Three female alignment channels 118 are further providedthat extend along the entire depth of the structure in the direction ofthe z-axis. The U-shaped cut-out region 120 has the added advantage ofminimizing the contact area and thus stress in the interface between thestructure and the bench or other surface to which it is attached.

[0047] In the illustrated implementation, each of the armatures 114A,114B comprises two segments 122 and 124. Specifically, and for example,armature 114B comprises two segments, 122B and 124B.

[0048] The vertically-extending segments 122A, 122B, i.e., extending atleast partially in the y-axis direction, have two flexures 126A, 126Balong their length, in the illustrated embodiment. These flexures areregions of reduced cross-sectional area in the segments, which regionsextend in the direction of the z-axis. The vertically-extending segments122 facilitate the positioning of an optical component, installed on theinterface 112, along the x-axis; the flexures 126A, 126B facilitate thepivoting of the segments 122A, 122B in a plane of the x and y axes. Apurpose of the flexures is to isolate regions of microstructural change,such as occurring in plastic deformation, in order to make the yieldforces, for example, readily predictable. Also, the flexures localizedeformation on the armatures and consequently decrease the amount offorce/movement required in the optical component before plasticdeformation is initiated in the armature.

[0049] Horizontally-extending (i.e., extending in the direction of thex-axis) segments 124A, 124B each comprise, in the illustratedembodiment, two flexures 128A, 128B. These flexures are also regions ofreduced cross-sectional area in the respective segments, the flexuresextending in the direction of the z-axis.

[0050] The horizontally-extending segments 124A, 124B allow thepositioning of an optical component, installed on the optical componentinterface 112, generally vertically along the y-axis. Armaturedeformation is facilitated by respective flexures 128A, 128B.

[0051] In one implementation, the optical component is bonded to theoptical component interface 112, and specifically bonding surface 132.This bonding is accomplished either through polymeric adhesive bondingor preferably solder bonding. In other implementations,thermocompression bonding, laser welding, reactive bonding or otherbonding method are used.

[0052] In the illustrated embodiment, the component interface furtherincludes structure-component alignment features 113. In the illustratedembodiment, the structure-component alignment features comprise slotsextending in the z-axis direction from the component bonding surface132. As a result, corresponding male-projections of an optical componentengage the slots 113 to locate and align the optical component over theoptical port 134 both along the x-axis and y-axis.

[0053] The optical component interface, in some implementations,comprises a port 134 for enabling an optical signal to pass transverselythrough the structure. This enables optical access to the opticalcomponent by either facilitating the propagation of an optical signal toand/or away from the component.

[0054] To facilitate the grasping and placement of the structure 100, ahandle 136 is also preferably provided on the structure. In theillustrated embodiment, the handle 136 comprises two V- or U-shaped cutout regions on either side, near the top of the top of the structure. Inthe illustrated example, they are integral with the optical componentinterface 112.

[0055] The handle 136 enables the manipulation of the structure 100 whenattached to the bench 10. Specifically, the right cut-out is engaged todisplace the structure to the left, for example. To displace thestructure vertically or in the y-axis direction, both cut-outs areengaged enabling the structure to be pressed down toward the bench 10 orpulled away from the bench.

[0056] To further facilitate grasping and installation on the bench,wing portions 121A, 121B are provided on each armature. These are usedby a heated vacuum chuck to enable manipulation of the structure andsubsequent heating for solder bonding. The short distance between thewings 121 and the base surface 116 facilitate good heat transfer.

[0057]FIG. 2 is a front plan view of the first embodiment of themounting and alignment structure 100, illustrated in FIG. 1. This viewillustrates the construction of the left and right armatures 114A, 114B,and specifically how the armatures are constructed from respectivehorizontally-extending segments 124 and vertically extending segments122.

[0058] Also shown is the extent of the bonding surface 132. Typically, asolder material is first applied to the surface 132. Later, the opticalcomponents and/or structures are heated and brought into contact witheach other to effect the solder bonding. In other embodiments, epoxybonding processes are used in which epoxy is first applied to thesurface 132.

[0059]FIG. 3A shows a second embodiment of the mounting and alignmentstructure. This embodiment shares a number of similarities with thefirst embodiment illustrated in FIGS. 1 and 2. Specifically, themounting surface 116 has slot-like alignment channels 118 for visualalignment.

[0060] Turning to the armatures 114A, 114B, vertically-extendingportions 122A, 122B are provided similar to the first embodiment. Twohorizontally extending portions 154, 155, however, are provided on eacharmature on each side of the mounting and alignment structure 100.Specifically, the armature 114B comprises two horizontally extendingsegments 154B, 155B, which extend generally from the verticallyextending portion 122B to the optical component interface 112.Specifically, a linkage portion 158B connects the distal ends both ofthe horizontally-extending portions 154B, 155B to thevertically-extending portion 122B of armature 114B.

[0061] The second embodiment of FIG. 3A illustrates a furtherconfiguration for the optical component interface 112. Specifically, theoptical interface 112 of the second embodiment comprises a V or U-shapedcut-out region or slot 152 extending through the mounting and alignmentstructure 100 in the direction of the z-axis. This open-slotconfiguration allows a fiber, schematically illustrated as F to beinstalled vertically in the direction of arrow 159 down into the slot152. In the typical implementation, the fiber F is then bonded to thesurface 132 in the bottom of the slot. Solder bonding is preferablyused, but other alternatives such as epoxy bonding exist.

[0062] In the preferred embodiment, the depth of the slot relative tothe locations of the attachment points of the armatures is designed toresist any rocking in response to z-axis forces exerted on the structureby the fiber. Specifically, some movement in response to z-axis forcesis unavoidable. Slot depth is controlled, however, so that the fiberaxis does not move in response to these forces.

[0063] In alternative embodiments, the handles 136 are engaged and theU-shaped slot crimped closed by applying force along arrow 157 to securethe optical component, such as fiber.

[0064]FIG. 3B shows exemplary dimensions of the third embodiment.Specifically, the height h of the illustrated embodiment is 1.1millimeters (mm). Generally the structures typically have height ofgreater than 0.5 mm to promote manipulation. To provide adequateclearance in standard packages, the structures are typically less then2.0 mm in height. The width w of the illustrated structure is 1.9 mm.Here again, the width is preferably greater than 0.5 mm to facilitatestable installation on the bench. To provide acceptable componentpacking densities and clearance between components the width w oftypically less than 4 mm is desirable.

[0065]FIG. 4 shows a third embodiment mounting and alignment structure100 that shares many similarities with the structures described inconnection with FIGS. 1-3. It has a base 110 and laterally-extendingbase surface 116. Further, the third illustrated embodiment has anoptical component interface 112 with an optical port 152. In thisexample, the handle 136 is more pronounced, extending vertically upwardfrom the interface 112.

[0066] V-shaped alignment features 210 are provided on the base surfacefor engaging complementary V-shaped alignment trenches in the bench.

[0067] One of the more distinguishing characteristics is the armatures114A and 114B. Instead of having segments that extend parallel to the xand y axes, each armature comprises two diagonally extending segments212, 214 that intersect substantially at a right angle with respect toeach other. Further, the armatures have no discrete flexure system butinstead have a relatively constant cross-section along the length of thearmatures.

[0068] Further, the optical component interface 112 comprises arelatively closed slot-shaped optical component mounting slot 152. Inone embodiment, a fiber is inserted into the slot 152 and then the slotis crimped closed to secure the fiber therein. Further, a handle 136 isprovided extending vertically from the optical component interface 112.In the illustrated example, the handle 136 has right and left extensionson either side of the slot 152.

[0069] Another distinction relative to the third embodiment of FIG. 4 isthe use of a z-axis flexure. Specifically, the base 110 comprises afront plate portion 422 and a rear plate portion (not shown). Thus, thebase 110 is a hollow box-configuration. The use of the Z-axis armatureallows controlled flexing when stress is exerted in a rotational manneraround the x-axis or θ direction.

[0070]FIG. 5A shows an embodiment in which the base is divided into twoseparate base portions 110A, 110B to promote a stable structure-benchinterface while simultaneously minimizing the contact area subject tothermal expansion mismatch stresses. In order to make the device morerobust during manufacturing of the structure and during its installationon the optical bench, a spring-like connecting element 310 connects thetwo halves of the base 110A, 110B. This element is clipped prior toinstallation or intentionally collapsed.

[0071]FIG. 5B shows a related embodiment with similar reference numeralsindicating similar parts. This embodiment is notable in that the anglebetween vertically-extending segments 126 and the horizontally-extendingsegments 124 form an obtuse angle. In some applications thisconfiguration facilitates alignment.

[0072]FIG. 6 shows a fifth embodiment, being closely related to thefourth embodiment of FIG. 5A. Here, the optical component interfacecomprises two separate, divided portions 112A, 112B. In this embodiment,an optical component, such as an optical fiber f is inserted into thevolumetric region between the two halves 112A, 112B of the interface.The two halves 112A, 112B are snapped closed around the fiber F.

[0073]FIG. 7 shows a sixth embodiment of a mounting and alignmentstructure. This embodiment is notable relative to the previouslydiscussed embodiments in that the armatures 114A, 114B have continuousflexures distributed across the length of the armatures. The flexuresare not located at specific flexure points as illustrated in some of theprevious embodiments. In this embodiment, the armatures act asdistributed flexing components that are subject to plastic deformation.

[0074]FIG. 8 shows a seventh embodiment of the mounting and alignmentstructures. This embodiment is notable in that the armatures 114A, 114Bare relatively rigid such that they will resist any flexing or plasticdeformation. Specifically, the armatures 114A, 114B have no discreteflexures as discussed relative to FIG. 1 nor do they have a continuousflexure system as illustrated in FIG. 7 as illustrated by the fact thatthe armatures are relatively thick. As a result, the embodiment of FIG.8 is typically used mostly for mounting fibers that pass outside of themodule or package through a fiber feed-through. The seventh embodimentresists strain to any stress exerted on, for example, a fiber F held inthe interface 112.

[0075] Typically, the seventh embodiment is used in conjunction with asecond mounting and alignment structure. The first mounting andalignment structure is proximate to the end of the fiber and enablesalignment of the fiber end in the x, y plane. The seventh embodimentalignment structure is used to minimize the stress transmitted throughthe fiber to the structure used for fiber-end alignment.

[0076]FIG. 9 illustrates an eighth embodiment with continuous flexurearmatures 114A, 114B and an optical interface 112 that would beappropriate for an optical component other than an optical fiber.Specifically, a mirror or lens is mounted on the optical interface 112by bonding such as solder or epoxy bonding. The port 134 enables opticalaccess to that component in which an optical signal is reflected by theoptical component or passes through the component thus also passingthrough the port 134.

[0077]FIG. 10 shows ninth embodiment where the base 110 is a relativelywide one-piece base.

[0078]FIG. 11 shows another embodiment in which four structures100A-100D are integrated on a common base 110. This system is useful forholding optical components, such as optical fibers for four physicallyparallel optical channels or paths. According to the invention, eachoptical fiber is separately aligned with separate alignmentcharacteristics of the structures. The common base, however, enablesmultiple, simultaneous passive alignment of the structures/fibers in asingle pick and placement step.

[0079]FIG. 12 shows a non-laterally symmetric mounting and alignmentstructure according to an eleventh embodiment. It comprises a base 110and an armature 114 extending from the base vertically. The armaturecomprises a vertical segment 122 and a horizontally extending segment124. The horizontally extending segment 124 terminates in a componentinterface 112. A handle 136 extends vertically from this interface.

[0080]FIG. 13 shows a non-laterally symmetric mounting and alignmentstructure according to a twelfth embodiment of the present invention. Inthis case, the base 110 extends in a vertical, y-axis direction suchthat it may be attached onto a side-wall of a module or another mountingand alignment structure. It further has a horizontally extendingarmature 114 and a component interface 112 adapted to hold a fiberconcentrically in the center or abut against a fiber to improve itsalignment.

[0081]FIG. 14 is a plan view of a mounting structure for exclusivelypassive mounting of an optical component. Specifically, the thirteenthembodiment has a base 112 and an integral optical component interface112. It further has a port 134 for enabling access to the opticalcomponent. This embodiment does not have armatures and consequently isonly susceptible to small alignment shifts. It is used mostly to holdcomponents when their horizontal or vertical positioning isnon-critical, such as, for example, a filter mirror in some systemdesigns.

[0082]FIG. 15A shows a mounting and alignment structure for mountingrelatively large MEMS filter device, in a current implementation.

[0083] Specifically, the fourteenth embodiment mounting and alignmentstructure has a divided base 110A, 110B. From each base, respectivearmatures 114A, 114B extend. The armatures each comprise a verticallyextending portion 122A, 122B and a horizontally extending portion 124A,124B. The optical component interface 112 is relatively large and isdesigned to hold an optical component mounted to the mounting surface132, for example. The handle 136 is integral with the interface in thisembodiment.

[0084]FIG. 15B illustrates the deployment of the fourteenth embodimentalignment structure 100B with one of the previously discussed alignmentstructures 100A. In typical installation and alignment, the mounting andalignment structure 100A is first installed on an optical bench 10.Alignment structure is then preferably deformed, in an active alignmentprocess, for example, such that the optical component is properlylocated relative to the optical path. Subsequently, after the alignmentof the optical component held by mounting and alignment structure 100A,the mounting structure 100B is installed with its own optical component.Then, this second alignment structure 100B is then tuned, in an activealignment process, for example, so that the second optical component isproperly located in the optical path. The relative size differencesbetween alignment structure 100A and 100B allows series alignments oftheir respective optical components even though the optical componentsare mounted in close proximity to each other on the bench 10.

[0085] Mounting Structure Manufacturing

[0086]FIGS. 16A-16C are cross-sectional views of the mounting andalignment structures 100 during the manufacturing process.

[0087] Specifically, as illustrated in FIG. 16A, a thick PMMA resistlayer 414 is bonded to a seed/release layer 412 on a substrate 410.

[0088] The depth d of the PMMA layer 414 determines the maximumthickness of the subsequently manufactured quasi-extrusion portion ofthe mounting and alignment structure. As a result, the depth determinesthe rigidity of the mounting and alignment structure 100 to forces alongthe Z-axis. In the preferred embodiment, the depth and consequentlyZ-axis thickness of the mounting and alignment structures is in therange of 500-1000 microns. Thicker structures are typically used forstrain relief-type structures. According to present processes, thestructures, and consequently the depth of the PMMA layer is as deep as2000 microns to produce structures of same thickness.

[0089]FIG. 16B illustrates the next fabrication step in the mounting andalignment structure 100. Specifically, the thick PMMA resist layer ispatterned by exposure to collimated x-rays. Specifically, a mask 416,which is either be a positive or negative mask having the desiredpattern for the structure, is placed between the x-ray source such as asynchrotron and the PMMA layer 414. The PMMA layer 414 is then developedinto the patterned layer 414A as illustrated in FIG. 16B.

[0090]FIG. 16C shows the formation of the quasi-extrusion portion of themounting structure 100. Specifically, in the preferred embodiment, thequasi-extrusion portion is formed via electroplating. The preferredplating metal is nickel according to the present embodiment. Nickelalloys, such as a nickel-iron alloy, are used in alternativeembodiments. Alternatively gold or a gold alloy is used in still otherembodiments. Currently, alternative metal and alloys include: silver,silver alloy, nickel copper, nickel cobalt, gold cobalt and alloys ladenwith colloidal oxide particles to pin the microstructures.

[0091]FIGS. 17A-17F illustrate a process of manufacturing the z-axisflexure 422 previously discussed with reference to FIG. 4. Specifically,as illustrated in FIG. 17A, after the formation of the quasi-extrudedportion of the mounting and alignment structure, the substrate 410 isremoved from the seed layer 412. Thereafter, an additional photoresist420 layer is coated and then patterned as illustrated in FIG. 17B forone plate of the z-axis flexure. Thereafter, a further electroplatingstep is performed to fabricate the plate of the z-axis flexure 422 ontothe existing cross-sectionally constant section 100.

[0092] In FIG. 17D, a second photoresist is formed and then patterned onthe reverse side of the structure 100 and first PMMA layer 414. Theetching is performed through the seed layer 412. Another plating step isperformed and the second plate of the z-axis flexure 428 is manufacturedas illustrated in FIG. 17E. Thereafter, as illustrated in FIG. 17F, theremaining photoresist layer 424, seed layer 412, and PMMA layer 414 areremoved leaving the hollow box-shaped structure illustrated. This boxshaped structure forms the bottom base section 422 of the mounting andalignment structure illustrated in FIG. 4.

[0093] Mounting Structure-Optical Component Bench Installation

[0094]FIG. 18A illustrates the process associated with installingoptical components on the optical bench 10.

[0095] The bench is preferably constructed from mechanically robust,chemically stable, and temperature stable material, such as silicon,beryllium oxide, aluminum nitride, aluminum silicon carbide, berylliumcopper. It is typically metal or ceramic coated with gold or a goldalloy for example.

[0096] Specifically, in a step 450, optical component 20 is installed ona first mounting and alignment structure 100-1. Specifically, theoptical component 20 is preferably bonded to the mounting and alignmentstructure 100-1. In the preferred embodiment, a solder bonding is usedin which solder is first applied to a periphery of the optical componentand/or the bonding surface 132 of the optical component interface 112.Then the optical component is brought into contact with the mountsurface 132 of the structure's component interface 112. The solder isthen melted and allowed to solidify.

[0097] Also in the preferred embodiment, complimentary alignmentfeatures in the optical component 20 and the interface 112 facilitatealignment and proper seating between the component 20 and structure100-1. Specifically, in alignment channels 113 (see FIGS. 1 and 2) areformed on the structure's interface. Marks or projections 451 on theoptical component 20 engage the slots 113 to ensure reproducibleinstallation of the component 20 on the structure 100-1.

[0098] In other embodiments, the component 20 is epoxy bonded or bondedusing another adhesive bonding technique to the structure.

[0099] Then, in a structure-bench mounting step 452, the structure 100-1is brought into contact with the optical bench 10 and bonded to thebench. In the preferred embodiment, solder bonding is used in which thebench is held in a heated chuck of a pick-and-place machine while thepreheated structure is brought into contact with the bench. The heat isthen removed to solidify the solder.

[0100] As illustrated in connection with alignment structure 100-2, forother optical components, the mounting steps are reversed. In thisexample, the mounting and alignment structure 100-2 is contacted andbonded to the bench in a structure-bench bonding step 454. Thereafter,the optical fiber F is seated in the U-shaped port 152 in step 457 ofthe mounting and alignment structure 100-2. Thereafter, the fiber iseither bonded to the interface bonding surface 132 or the U-shaped slotis crimped such that the fiber is secured in the bottom of the U-shapedport. Thus, the fiber endface EF is secured to the optical bench inproximity to the optical component, such as thin film filter or mirror20, held by structure 100-1.

[0101]FIG. 18B also illustrates the process associated with installingMEMS-type optical components on the optical bench 10. Specifically, inthis embodiment, a front mirror 470 is first bonded over a reflectivemembrane of the MEMS device 472 in a first bonding step 474. Then, theMEMS device 472 is bonded to the alignment structure 100 in a secondbonding step 476. Then in a bench-bonding step 478, the compositeMEMS/structure is bonded to the bench 10.

[0102] Mounting Structure Deformation in Alignment

[0103]FIG. 19 is a perspective view of a fiber optic laser opticalsignal source system, which has been constructed according to theprinciples of the present invention. Specifically, the laser sourcesystem 610 comprises a laser chip 612, which has been mounted on ahybrid substrate 614. Typically, this substrate supports the electricalconnections to the chip 612 and possibly also comprises a thermoelectriccooler for maintaining an operating temperature of the chip 612. Thehybrid substrate 614 is in turn installed on an optical bench portion 10of a package substrate 622. A detector 616 is located behind the chip612 on the bench 10 to detect rear facet light and thereby monitor theoperation of the laser 612.

[0104] Light emitted from a front facet 618 of the chip 612 is collectedby a fiber f for transmission outside the optical system 610. In oneimplementation, the light propagating in fiber f is used to opticallypump a gain fiber, such as a rare-earth doped fiber or regular fiber ina Raman pumping scheme. In other implementations, the laser chip 612 ismodulated in response to an information signal such that the fibertransmits an optical information signal to a remote detector. In stillother implementations, the laser chip 612 is operated to run in a CWmode with modulation performed by a separate modulator such as aMach-Zehnder interferometer.

[0105] An optical component mounting and alignment structure 100,according to the invention, is installed on the optical bench portion 10of the package substrate 622. As discussed previously, the optical benchhas alignment features 620, which mate with opposite-gender alignmentfeatures on the base surface of the mounting and alignment structure 100as described previously in connection with FIG. 1, for example.

[0106] As also discussed previously, the fiber f is installed in theU-shaped port 152, which is part of the optical component interface 112of the mounting and alignment structure 100.

[0107]FIG. 20 is a process diagram illustrating the active alignmentprocess that is used in conjunction with the deformable opticalcomponent mounting structures in the manufacture of an optical signalsource as illustrated in FIG. 19, for example.

[0108] Specifically, in step 650, a laser die 614 and alignmentstructure 100 are mounted to the optical bench 10 in a pick-and-placeand bonding process. Specifically, a pick-and-place robot locates thedie 614 and the alignment structure 100 on the optical bench 10 usingpassive alignment. The alignment process is preferably accomplishedusing machine vision techniques and/or alignment features in the laserbench 10, and mounting and alignment structure 100, and die 614, orexplicitly relative to a defined coordinate system of the bench10/module 622.

[0109] In step 652, once the laser hybrid 614 and structure 100 areattached to the bench 10, wire bonding is performed to the laser hybrid.Then, in step 654, the laser 612 is electrically energized to determinewhether or not the laser is functioning properly.

[0110] If the laser is not functioning, then the optical system isrejected in step 656.

[0111] If, however, the laser is determined to be operational in step654, the bench is moved to an alignment fixture of the production systemin step 658.

[0112] In step 660, the fiber f is inserted into the U-shaped port 152of the optical component interface 112 and bonded there. In thepreferred embodiment, the fiber is solder bonded to bonding surface 132.

[0113] In step 664, the alignment system grasps or engages the mountingand alignment structure 100 to deform the mounting and alignmentstructure 100 in response to a strength or magnitude of a signaltransmitted by the fiber f from the laser 612.

[0114]FIG. 21 illustrates the engagement between the alignment systemand the mounting and alignment structure 100 to align the fiber f.Specifically, the two jaws 710A, 710B engage the handles 136 of themounting and alignment structure 100 and then move the mounting andalignment structure to displace the fiber f in an x-y plane, which isorthogonal to the axis of the fiber f. Simultaneously, the magnitude ofthe signal transmitted by the fiber is monitored until a maximum signalis detected in step 666 of FIG. 20. Of note is the fact that the rightand left cut-outs of the handle 136 enable the jaws of alignment systemto both pull and push the structure away and toward the bench 10, asneeded to achieve an optimal alignment.

[0115] Returning to FIG. 20, once the maximum signal is detected in step666, the alignment system further deforms the mounting and alignmentstructure 100 such that when the mounting and alignment structure isreleased, it will elastically snap-back to the desired alignmentposition detected in step 666. In other words, the mounting andalignment structure is plastically deformed such that it will haveproper alignment when the jaws 710A, 710B of the alignment systemdisengage from the mounting and alignment structure 100.

[0116] If it is subsequently determined in step 670 that the opticalcomponent, i.e., the fiber is not at the position associated with themaximum coupling, the deformation step 668 is performed again until theposition is within an acceptable tolerance.

[0117]FIG. 22 is a plot illustrating the alignment process.Specifically, the figure of merit or the coupling efficiency of lightinto the optical fiber is plotted as a function of displacement of theoptical fiber. Specifically, the coupling efficiency is maximized whenthe fiber is located at the best alignment position and falls off oneither side of this position.

[0118]FIG. 22 also illustrates force or stress as a function of strainor displacement during the several steps of the alignment process.Specifically, in a first step 710, force is exerted on the mounting andalignment structure, such that it undergoes elastic deformation. In thisregime, there is a substantially linear relationship between the appliedforce, on the y-axis and the displacement or strain on the x-axis. Oncethe yield force level is exceeded, however, the mounting and alignmentstructure 100 undergoes plastic deformation as illustrated by line 720.This plastic deformation results in permanent deformation to themounting and alignment structure.

[0119] When force is removed, the mounting and alignment structureundergoes elastic “snap-back” as illustrated by step 722. That is, withthe force removed, the structure undergoes some elastic movement.However, because the yield force level was exceeded, the mounting andalignment structure has been permanently deformed as indicated bydistance Δ₁.

[0120] Even with this plastic deformation, the fiber is still not at thebest alignment position. As a result, another cycle of plasticdeformation is performed. Specifically, force is applied such that themounting alignment structure undergoes elastic deformation asillustrated by line 724. Once the new yield force level has beenexceeded a second time, it then undergoes plastic deformation asindicated by line 726. The yield force has increased during this secondalignment cycle due to work hardening. Force is then removed and themounting and alignment structure undergoes elastic snap-back asillustrated by line 728.

[0121] This second plastic deformation step, since it exceeded the yieldforce, resulted in movement toward the best alignment position of Δ₂.

[0122] Nonetheless, if optimal alignment is to be achieved, more plasticdeformation must be performed. Specifically, again the elasticdeformation is performed in step 730 until the yield force is reached.Then, a small amount of plastic deformation is performed as indicated byline 732. Force is removed and the mounting alignment structure nowsnaps back to the best alignment position as indicated by line 734.

[0123] The graph insert shows the figure of merit during the alignmentprocess. During the first plastic deformation cycle, the position passesthrough the best alignment position, but after force is removed, theelastic snap-back pulls it out of best alignment. During the seconddeformation cycle, the best alignment position is again passed andexceeded. This second cycle, however, improves the alignment once forceis removed. Finally, the third cycle brings the fiber into the bestalignment position.

[0124] Mounting Structure Design Criteria

[0125]FIG. 23 presents a plot of force, F_(Y), as a function ofdisplacement that can be employed in accordance with the invention todesign the armatures for a given application. The yield force is theforce at which the structure begins to undergo plastic deformation froman elastic deformation regime.

[0126] The lower bound on F_(Y) (1200) is constrained by environmentalshock, i.e., acceleration, and by the possible forces to which themounting structure might be subjected during handling. Somespecifications require optical systems to withstand 5000 g shock-tests.Typically with some optical elements, yield forces of greater than 0.5Newtons are typically required. This number, however, can be reduced asthe size and thus mass of optical elements is reduced. Were there nominimum yield force constraint, the unavoidable forces produced duringhandling, including fabrication, heat treatment, plating, pick andplace, alignment, packaging, and other processes, could cause plasticdeformations of the flexure joints. More seriously, any shock to analigned system might misalign it, defeating one of the purposes of theinvention.

[0127] The upper bound on F_(Y) (1250) is constrained by three factors.First, the force required to cause plastic deformation of an armature orflexure must not be so high as to weaken or destroy the bond between themounting structure and the substrate. Second, the yield force must notbe so high as to cause significant elastic deformation in themicromanipulator that is applying the force. Third, the force requiredto deform the armature or flexure must not be so high as to damage otherportions of the integrally-formed mounting structure.

[0128] In addition to constraining the armature yield force, it is alsopreferred to constrain how much displacement is required in order toreach the yield point. The lower bound (line 1300) is dictated first bythe physical range of the structure. A mounting structure only functionsas desired if there is enough plastic deformation range to reach thealigned position. Generally, the alignment structures need to enablemovement or placement of the optical component of 0 to 50 microns. Thetypically alignment algorithms require plastic deformation that yields 4to 5 microns of movement in the position of the optical component toreach alignment. The second constraint on the minimum stiffness isdetermined by the amount of “overshoot” deemed acceptable by thealignment algorithm. If the structures are too elastic, then they mustbe pressed a long distance beyond the desired alignment point in orderto make even a small alignment adjustment.

[0129] The final constraint is the maximum stiffniess of the flexures(line 1350). Were work hardening not an issue, there would be noconstraint on maximum stiffness (except, of course, materiallimitations). With nickel and nickel alloys, however, work hardeningoccurs. Therefore, the stiffness upper bound is selected so that line1250 is not exceeded even with work hardened created by successiveplastic deformation cycles performed during the search for the correctalignment.

[0130] In the preferred embodiment, F_(Y, y), i.e., the yield force inthe direction of the y-axis, is less than 3 Newtons (N), typicallybetween 0.2 and 1 N. The yield force along the x-axis, F_(Y, x) issimilarly limited to less than about 3 Newtons, typically between 0.2and 1 N. Yield forces below 0.2 N are viable if smaller opticalcomponent are used, however. These lower limits are related to the massof the optical component that the structure must restrain withoutunintended plastic deformation. Thus, lower yield forces are possiblewith smaller components in subsequent product generations.

[0131] In contrast, the yield force the z-axis direction, i.e., F_(Y, z)or F_(Y, θ), is much larger to promote alignment in only the x-y plane.Preferably, F_(y, z) or F_(y, θ) are greater than 5 N or 10 N. Further,especially in versions of the alignment structures that are used tosecure fiber pigtails to benches. Thermal expansion mismatches resultingstresses on the fibers. The objective is to design the structures sothat such stresses result in as little movement in the fiber endface aspossible. Especially any rocking motion is desirably avoided bybalancing the structures by selecting the location of where thearmatures attach to the fiber component interface.

[0132] Further Embodiments

[0133]FIG. 24 illustrates another embodiment of the invention in whichthe structure 100 is a composite of an extrusion-like portion 101, whichhas a constant cross section along the z-axis, and two z-axis flexurepieces 102, which control rotation around the x-axis or in the directionof angle Θ_(x), thereby determining the resistance to force componentsalong the z-axis. Preferably on the z-axis flexure pieces 101 areseparately fabricated and bonded to base surface of portion 101. Basesurfaces of the pieces are then bonded to the bench.

[0134]FIG. 25 is an example mounting structure provided by the inventionwherein two different materials (indicated as “A” and “B”) are employedin the mounting structure for minimizing any change in optical axislocation due to thermal expansion and/or contraction of the structure.In one example configuration, the “A” material is selected, incombination with the design of that region of the structure, to expandupward due to temperature change, while the “B” material and itscorresponding mounting design features are selected for a tendency toexpand downward due to temperature change. These opposing expansiontendencies result in a compensating action that produces stability instructure geometry and position across a range of operationaltemperatures.

[0135] Optical System Production Line

[0136]FIG. 26 schematically illustrates the manufacturing sequence foroptical systems according to the principles of the present invention.Generally, process comprises precision pick and place to locate theoptical component to an accuracy of better than 10 microns, better thantwo microns in the preferred embodiment, followed by active alignment inwhich the position of the component is trimmed to an accuracy of about amicron, preferably better than a micron.

[0137] Specifically, an alignment structure supply 2010, such as a gelpack or other machine-vision compatible holder, is provided along with asimilarly configured optical component supply 2012.

[0138] Each of the supplies is accessed by a pick-and-place machine2014. Specifically, the pick-and-place machine applies the opticalcomponents to the alignment structures and bonds the components.Typically, either the alignment structures and/or the optical componentsare solder coated or solder performs are used. The pick-and-placemachine heats the alignment structure and the optical components andbrings the two pieces into contact with each other and then melts andresolidifies the solder.

[0139] In the current embodiment, the pick-and-place machine ismanufactured by Karl Süss, France, type FC-150 or FC-250. Thesepick-and-place machines have a vacuum chuck for picking-up the opticalcomponents and a holder for holding the alignment structures.

[0140] The alignment structures, with the affixed optical components arethen fed to a separate or the same pick-and-place machine, which hasaccess to an optical bench supply 2018. In this second pick-and-placeoperation, the pick-and-place machine 2016 holds the optical bench on avacuum chuck or holder and then applies the alignment structure, withthe optical component, to the optical bench using its vacuum chuck. Thebench and structure are then heated to effect the solder bonding.Further, by matching alignment features of the benches and alignmentfeatures of the mounting structures, placement accuracies of less than 5microns are attainable. In the preferred embodiment, the structures arelocated on the bench with accuracies of better than 2-3 microns in aproduction environment.

[0141] In the preferred embodiment, the optical benches, with thealignment structures affixed thereto are then fed to an alignmentsystem. This alignment system 2020 has the jaws 710A, 710B which graspthe handle of the alignment structure 100 to effect alignment. In thepreferred embodiment, this alignment is active alignment in which themagnitude of the optical signal 2022 is detected by a detector 2024. Thealignment structure 100 is manipulated and deformed until the opticalsignal 2022, detected by the detector 2024, is maximized. Alignmentsearch strategies such are a hill-climbing approach or spiral scanapproach are preferably utilized.

[0142] In other situations, such as when installing optical fibers onthe bench 10, the alignment structure is preferably installed firstwithout the fiber attached by the pick and place machine 2016. Then atthe alignment system, the fiber is fed through a fiber feed-through inthe module and attached, such as by solder bonding, to the alignmentstructure 100. Then the alignment system manipulates the structure toeffect alignment.

[0143] Once aligned, the optical bench and module is then passed to alid sealing operation 2026 where the final manufacturing steps areperformed such as lid sealing and baking, if required.

[0144]FIGS. 27A, 27B, and 27C illustrate three different configurationsfor the alignment channels 118 introduced in FIG. 1.

[0145]FIG. 27A is the simplest design, but has a drawback associatedwith implementation in machine vision applications when the base surfaceis pre-coated with solder, or other bonding agent. Solder fills in thecreases and smoothens the channel's edges making alignment based on thefeatures potentially less accurate.

[0146]FIGS. 27B and 27C show channels incorporating cavities in thefeatures that facilitate the identification of edges 118A even aftersolder coating. The resulting clear edge features, even after coating,facilitate alignment during bench installation.

[0147] While this invention has been particularly shown and describedwith references to preferred embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the scope of the inventionencompassed by the appended claims.

What is claimed is:
 1. An optical system production method, comprisingsupplying optical benches from an optical bench supply; supplyingoptical components from a component supply; receiving optical componentsfrom the optical component supply and optical benches from the opticalbench supply at a pick-and-place machine; attaching the opticalcomponents to the optical benches with the pick-and-place machine;characterizing positions of the optical components, which have beenattached to the optical benches; and mechanically adjusting the relativepositions of the optical components with an optical system aligner. 2.An optical system production method as claimed in claim 1, wherein thestep of attaching the optical components to the optical benches with thepick-and-place machine comprises solder bonding the optical componentsto the optical benches.
 3. An optical system production method asclaimed in claim 1, wherein the step of characterizing the positions ofthe optical components comprises: the optical system aligner activatingoptical links of optical systems; detecting optical signals afterinteraction with at least some of the optical components; and adjustingthe optical components to optimize transmission of the optical signalsin the optical systems.
 4. An optical system production method asclaimed in claim 1, wherein the step of characterizing the positions ofthe optical components comprises: energizing active components ofoptical systems; and adjusting the optical components to optimizeoptical signal transmission through the optical systems from the activeoptical components.
 5. An optical system production method as claimed inclaim 1, wherein the step of characterizing the positions of the opticalcomponents comprises: energizing active components of optical systems;and adjusting a position of at least one passive optical component ineach of the optical systems to optimize optical signal transmission fromthe active components through the optical systems.
 6. An optical systemproduction method as claimed in claim 1, wherein the step ofcharacterizing the positions of the optical components comprises:energizing active components of optical systems; and adjusting positionsof at least two passive optical components in each of the opticalsystems to optimize optical signal transmission between the passivecomponents.
 7. An optical system production method as claimed in claim1, wherein the pick and place machine is a flip-chip bonder.
 8. Anoptical system production method as claimed in claim 1, wherein the stepof mechanically adjusting the relative positions of the opticalcomponents comprises engaging mounting structures supporting the opticalcomponents and moving the structures relative to the optical bencheswith the optical system aligner.
 9. An optical system production methodas claimed in claim 1, wherein the step of mechanically adjusting therelative positions of the optical components comprises engaging mountingstructures supporting the optical components and plastically deformingthe structures relative to the optical benches with the optical systemaligner.
 10. An optical system production method as claimed in claim 1,further comprising attaching optical components to mounting structuressupplied from an alignment structure supply.
 11. An optical systemproduction method, comprising supplying optical benches from an opticalbench supply; supplying optical components from a component supply;supplying mounting structures from an alignment structure supply;attaching the optical components to the mounting structures at a pickand place machine; receiving optical components, attached to themounting structures, and optical benches from the optical bench supplyat a pick-and-place machine; attaching the optical components to theoptical benches, via the mounting structures, with the pick-and-placemachine; characterizing positions of the optical components, which havebeen attached to the optical benches; and mechanically adjusting therelative positions of the optical components with an optical systemaligner by deforming the mounting structures to which the opticalcomponents are attached.